While document copiers have become prolific, there are certain situations where it becomes highly desirable to prevent the copying of specific originals. Such situations could occur, for example, with the illicit or unauthorized photocopying of classified or proprietary documents.
The problem of illicit photocopying of classified or proprietary documents has become pandemic. It would be highly desirable to be able to inhibit the xerographic or other type reproduction of sensitive documents. To do so requires that the photocopier be equipped with a detection and control system that will inhibit the copier automatically before the image can be captured electrostatically, unless a proper "enable" signal is received. This becomes especially important when the frequent occurrence of government espionage activities is considered in which illicit photocopies have been made of very highly classified documents. Recently, there have been a number of publicly reported cases wherein copies of information regarding battle plans fleet dispositions, communication frequencies, corporate strategies, merger plans, sales histories/forecasts, new product development reports, etc., have been sold on the open market. The ability to prevent the unauthorized photocopying of selected documents becomes extremely important to both national security and the potential future of many corporate activities and entities.
This problem can be solved by a technique which is referred to herein as the Zerosafe.TM. process. The technique utilizes the application of unique phosphors to paper. The phosphors may be applied either to the surface of the paper in a postproduction facility, or incorporated into the paper during the last stages of paper making. The latter technique would be preferable since it would greatly reduce the possibility of removing the phosphors without significantly damaging the paper itself.
One alternative is to utilize conventional phosphors. Another alternative utilizes what are known as upconversion phosphors. Since the upconversion phosphors are significantly less common than conventional phosphors, a Zerosafe.TM. implementation utilizing this approach incorporates a number of unique advantages which are discussed herein.